In severe spinal deformity, complex revision spine surgery, and patients with compromised bone stock, bone screw fixation to vertebral bodies can be problematic and less than optimal. Screw pullout and lack of fixation points can limit the surgeon's ability to safely and adequately complete fixation.
Current and past vertebral fixation devices generally depend on uni- or bilateral fixation of bone screws to vertebral bodies. The bone screws are generally inserted into vertebral bodies, but have no anchor point within the vertebral body, and therefore can suffer from screw pullout.